Cooley's Cyclopaedia of Practical Receipts Volume I Part 18

Carbonic Acid Volume of Size of bottle Size of bottle in the Air, Air in cubic in cubic in ounces per cent. centimetres. centimetres. Avoirdupois.

03 185 199 706 04 139 154 542 05 111 125 444 06 93 107 378 07 79 93 331 08 70 84 296 09 62 76 269 10 56 70 246 11 51 65 229 12 46 60 214 13 43 57 201 14 40 54 190 15 37 51 181 20 28 42 148 25 22 36 129 30 19 33 116 40 14 28 104 50 11 25 89 60 9 23 89 70 8 22 78 80 6 20 72 100 55 197 70

Mr w.a.n.klyn's process for the determination of carbonic acid in the atmosphere is as follows:--A solution of carbonate of soda is first made as follows: 447 grammes of gently-ignited carbonate of soda are dissolved in one litre of water, giving a solution of such a strength that 1 c. c.

contains exactly 1 c. c. of carbonic acid (= 197 milligrammes of CO_{2}); a large quant.i.ty of baryta water (strength about 01 per cent.) is prepared.

If now 100 c. c. of clear baryta water be treated with 1 c. c. of carbonate of soda, just described, a certain degree of turbidity is produced.

If 2 c. c. of the solution be taken another degree of turbidity is produced, and so on. If, then, a bottle capable of holding 2000 c. c. of air, together with 100 c. c. of baryta water, be filled with the sample of air to be tested, there will be a certain depth of turbidity produced by shaking it up. Having got the air to expend itself on 100 c. c. of baryta water the degree is to be found by comparison with another 100 c. c. of baryta water, in which a like turbidity has been induced by means of the standard solution of carbonate.

Every c. c. of soda solution counts for a c. c. of carbonic acid in two litres of air. A consumption of 1 c. c. will correspond to 05 volumes of carbonic acid per cent. Good air should accordingly not take more than 1 c. c. of soda solution, air which takes already 2 c. c. being already bad.

In order practically to carry out this method of estimating carbonic acid the following apparatus is required:--Several bottles capable of holding 2210 c. c., and well stoppered (failing bottles of exactly the right capacity Winchester quart bottles will answer); a small pair of bellows; several colourless gla.s.s cylinders marked at 100 c. c. capacity--the Nesslerising cylinders will answer for this purpose--a graduated pipette or burette to deliver tenths of a c. c. of solution, the standard solution of carbonate of soda, and the baryta water, which may be of moderate strength.

The testing is managed thus: Winchester quart bottles having been made clean are rinsed with distilled water, and allowed to drain a little. They are then closed with their stoppers, and are ready for use. The operator having provided himself with two or three of these bottles and a small pair of bellows enters the room the air of which is to be tested. The stopper is then removed from one of the bottles, and some air of the room blown through with the bellows, and then the stopper is replaced, and the bottle carried away to be tested.

The testing is done by pouring into the bottle 100 c. c. of clear baryta water, shaking up for two or three minutes, and then pouring out into a cylinder of colourless gla.s.s, and observing the depth of the turbidity in various lights and against various backgrounds. The turbidity is to be exactly imitated by means of the standard solution of carbonate of soda.

In order to imitate the turbidity produced by a Winchester quart full of good air only 1 c. c. of this solution of carbonate of soda is required.

If 2 c. c. or more than 2 are required, the air is bad and the ventilation is defective.

In place of the first c. c. of solution of carbonate of soda the carbonic acid naturally present in a Winchester quart of good average air may be used, and a little practice and intelligence will suggest the necessary precautions.

_Estimation of the Oxygen._--To determine this Angus Smith has recourse to the endiometer. Five or six of Bunsen's endiometers were used at once and the mixed gases were exploded by means of a powerful battery and a Ruhumkorff's coil. In his 'Inorganic Chemistry,' Miller thus explains the principle upon which the action of the endiometer is based: "By means of the endiometer various gaseous mixtures may be a.n.a.lysed with great exactness. Many different forms of this instrument are in use. One of the most convenient is Hoffmann's. It consists of a stout syphon tube. (See next figure.) Into the sides of the tube, near the sealed end, two platinum wires (_a_, _b_) are fixed for the purpose of transmitting an electric spark through the cavity of the tube. The sealed limb is accurately graduated to tenths of a c. c. or other suitable divisions.

Suppose it be desired to ascertain the proportion of oxygen in atmospheric air. The instrument is first filled with mercury, after which a small quant.i.ty of air is introduced; the bulk of the air is accurately measured, taking care that the liquid metal stands at the same level in both tubes, which is easily effected by adding mercury, or by drawing off the mercury if needed, through the caoutchouc tube, which is fixed upon the small inlet tube just above the bend, and which is closed by means of a screw tap (_c_).

[Ill.u.s.tration]

A quant.i.ty of pure hydrogen, about equal in bulk to the air, is next introduced, and the bulk of the mixture is then accurately measured. The open extremity of the tube is now closed with a cork, below which a column of atmospheric air is safely included. This portion of air acts as a spring, which gradually checks the explosive force, when the combination is effected by pa.s.sing a spark across the tube by means of the platinum wires. The mixture is then exploded by the electric spark. The remaining gas now occupies a smaller volume, owing to the condensation of the steam which has been formed. Mercury is, therefore, again poured in the open limb until it stands at the same level in both tubes, and the volume of the gas is measured a third time. One third of the reduction of the bulk experienced by the gas will represent the entire volume of oxygen which the mixture contained. Liebig's method is as follows. It is based upon the fact that an alkaline solution of pyrogallic acid absorbs oxygen:

1. A strong measuring tube holding 30 c. c., and divided into one fifth or one tenth c. c., is filled to two thirds with the air intended for a.n.a.lysis. The remaining part of the tube is filled with mercury, and the tube is inverted over that fluid in a tall cylinder widened at the top.

2. The volume of air confined is measured--a quant.i.ty of solution of potash of 14 sp. grf. (1 part of dry hydrate of potash to 2 parts of water), amounting from 1/40th to 1/50th of the volume of the air, is then introduced into the measuring tube by means of a pipette with the point bent upwards (see _drawing_), and spread over the entire inner surface of the tube by shaking the latter. When no further diminution of volume takes place the decrease is read off. The carbonic acid is thus removed.

[Ill.u.s.tration]

3. A solution of pyrogallic acid containing 1 gramme of the acid in 5 or 6 c. c. of water is introduced into the same measuring tube by means of another pipette similar to the above. The mixed fluid (the pyrogallic acid and the solution of potash) is spread over the inner surface of the tube by shaking the latter, and when no further diminution of volume is observed the residuary nitrogen is measured.

4. The solution of pyrogallic acid mixing with the solution of potash of course dilutes it, causing thus an error from the diminution of its tension; but this error is so trifling that it has no appreciable influence upon the results. It may, moreover, be readily corrected by introducing into the tube, after the absorption of the oxygen, a small piece of hydrate of potash, corresponding to the amount of water in the solution of the pyrogallic acid.

There is another slight error on account of a portion of the fluid adhering to the inner surface of the tube, so that the volume of the gas is never read off with absolute accuracy.

In conducting these endiometric experiments the necessary corrections for temperature and barometric pressure must, of course, be made.

_Estimation of the Nitrogen._ The amount of this gas is usually determined by deducting the aqueous vapours, oxygen and carbonic acid, from the volume of air examined.

_Determination of Ammonia and Organic Matter._ These are best determined by drawing a known volume of air through absolutely pure water. To obtain this latter it is best to redistil distilled water, to reject the first portions, then to add an alkaline solution of permanganate of potash, and to discard any portions of the distillate which give the slightest reaction with the Nessler test. The water through which the air is drawn must be kept cool, and afterwards submitted to the proper tests, which will be found under AMMONIA and WATER a.n.a.lYSIS. Mr Blyth says, "Solid bodies such as vibrionic germs, dust, fungi, &c., may be obtained by using an aspirator, and drawing the air either through a drop of glycerine or water. Organic matter may also be obtained by suspending gla.s.s vessels filled with ice water, over or in the places to be investigated, and submitted to the microscope. High powers, such as immersion lenses, are requisite for the investigation of germs," &c.

Of these germs Dr Angus Smith says:--"They may probably be divided into many kinds--the useful and the deleterious, those which promote health and those which bring disease. The idea of any of them bringing health is not founded on anything positive, but we can scarcely imagine these numberless forms to be all useless. The idea that they bring disease is, I think, one well confirmed." See a paper by the same author "On the Air and Rain of Manchester." 'Memoirs of the Literary and Scientific Society of Manchester,' vol. x. See AIR, VITIATED.

=AIR-GAS.= Air deprived of its carbonic acid and moisture, and then impregnated with the vapours of very volatile fluid hydrocarbons, such as benzine and benzoline, can be used as an illuminating agent. It is requisite, however, to use burners with wide openings, and to apply a low pressure, because if the current be too rapid the flame becomes too much cooled, and is readily extinguished. Apparatus for preparing air-gas have been devised and constructed by Marcus, Mille, Methei, and others.

[Ill.u.s.tration]

=AIR-PUMP.= An instrument designed for the removal of air from closed vessels. The simplest form of air-pump is the exhausting syringe, which consists of a cylinder fitted with a stop-c.o.c.k, and having a valve at the bottom opening inwards. Another valve opening outwards is attached to a piston working inside the cylinder, and by s.c.r.e.w.i.n.g the instrument on to a vessel, and alternately elevating and depressing the piston, all except a very small quant.i.ty of residual and comparatively inelastic air is pumped out of the vessel (Figs. _a_ and _b_). The accompanying figures show relative positions of the valve during (_a_) the elevation, and (_b_) the depression of the piston. In the usual and more convenient form of air-pump, a bra.s.s tube pa.s.ses from the bottom of the syringe and terminates in the centre of a disk of bra.s.s or gla.s.s ground accurately; the vessel from which the air is to be exhausted has its edge very accurately ground, and is mounted upon the plate as shown in the subjoined figure.

[Ill.u.s.tration]

=Air-pump, Bunsen's Water.= (See figure on page 53.)

This consists of a wide gla.s.s tube, _a_, into which another tube, _b_, _b'_, _b"_, pa.s.ses air-tight. _c_ is an india-rubber tube connecting a with the water supply, _d_ is a clamp to stop the flow of water through _c_. _e_ is another clamp to regulate the flow, _f_ is a reservoir to prevent any water which may accidentally come over from getting into _j_.

_g_ is a plug to let out any water from _f_. _h_ is a screw for connecting a air-tight to a piece of tubing, which should pa.s.s 32 feet, if possible, below the level of _a_. _i_ is a piece of strong india-rubber tubing to connect the pump with the vessel to be exhausted. The water rushes in at _c_ and down _h_, carrying bubbles of air with it till the exhaustion is complete. The figure ill.u.s.trates a common application of this pump to the rapid filtration of liquids which ordinarily pa.s.s through paper with difficulty. _a_ is represented as being about half full of water. _k_ is a funnel fixed air-tight in the india-rubber stopper of the bell-jar _j_.

_l_ is a small cone of platinum foil to prevent the paper filter which fits into it from being broken. _m_ is a plate of ground gla.s.s, _n_ is a beaker to receive the filtrate.

[Ill.u.s.tration: Bunsen's water-air-pump.]

=Air-pump, Sprengel's.= This apparatus depends on the principle of converting the s.p.a.ce to be exhausted into a torricellian vacuum.

In the subjoined figure, _c_, _d_ is a gla.s.s tube longer than a barometer, open at both ends, and connected by means of india-rubber tubing with a funnel, A, filled with mercury and supported by a stand. Mercury is allowed to fall in this tube at a rate regulated by a clamp at C; the lower end of the tube, _c_, _d_, fits in the flask B, which has a spout at the side a little higher than the lower end of _c_, _d_; the upper part has a branch at _x_ to which a receiver R can be tightly fixed. When the clamp at C is opened, the first portions of mercury which run out close the tube and prevent air from entering below. As the mercury is allowed to run down the exhaustion begins, and the whole length of the tube from _x_ to _d_ is fitted with cylinders of air and mercury, having a downward motion. Air and mercury escape through the spout of the bulb B, which is above the basin H, where the mercury is collected. It is poured back from time to time into the funnel A, to be repa.s.sed through the tube until the exhaustion is complete.

[Ill.u.s.tration: Sprengel's air-pump.]

=AIRY'S (Dr.) NATURE'S MEDICAL TREATMENT= is the t.i.tle of a pamphlet which recommends four secret remedies against 166 diseases:

_a._ The Pain Expeller, a mixture of about 35 parts of tincture of capsic.u.m, 20 parts of diluted spirit, and 20 parts of spirit of ammonia.

_b._ Sarsaparillian, a fluid extract of sarsaparilla and China root, containing 1 per cent. of iodide of pota.s.sium.

_c._ Pills composed of powdered iron, jalap resin, jalap powder, and marsh mallow powder, made into a ma.s.s with some bitter extract. Each pill weighs 01 gramme.

_d._ Calming Pastilles are thick, hard tablets, composed of sugar, with oil of anise, and coloured with liquorice juice. (Hager.)

=AKUSTICON= (an ear essence). A proved remedy for every kind of ear disease, by Pserhofer. This may be imitated by dissolving in common glycerine one fifth of its weight of fir tar, filtering, and adding a few drops of cajeput oil dissolved in spirit (Hager.)

=AL-.= [Ar.] An inseparable article equivalent to the English _the_. It is found in many chemical and other words derived from the Arabic; as alchemy, alcohol, alembic, almanac, &c.

=AL'ABASTER.= _Syn._ ALBaTRE, Fr.; =Alabas'ter=, =Alabastri'tes=, =Alabas'trum=, L. A soft, white species of calcareous and of gypseous stone, used by sculptors. There are several varieties, all of which may be ranged under two heads:--

1. CALCA"REOUS ALABASTER; ORIENT'AL, A.; CALC-SIN'TER. A sub-variety of carbonate of calcium, formed by the deposition of calcareous particles in the caverns of limestone rocks. It has a foliated, fibrous, or granular structure, and a pure, soft, rich, semi-translucent whiteness, generally agreeably variegated with undulating zones or stripes of various shades of yellow, red, or brown. This variety is that most esteemed by sculptors, and for the manufacture of alabaster ornaments. The ancients used it for ointment and perfume boxes. At the baths of San Filippo (Tuscany), the process of its formation may be examined by the observer. The natural spring of boiling water holds carbonate of lime in solution by means of sulphuretted hydrogen, which, escaping into the air, leaves the lime as a precipitate, which is gradually deposited in a concrete form. (M. Alex.

Brogniart.)

2. GYP'SEOUS OR COMMON ALABASTER; GYPSUM. A natural hydrated sulphate of calcium, containing a little carbonate of calcium. That from the quarries of the Paris basin contains about 12% of the latter substance. When calcined or roasted, and powdered, it forms the substance known under the name of PLASTER OF PARIS. The more compact, fine-grained specimens of this variety are, like the preceding one, sculptured into almost numberless articles of ornament and utility, such as vases, clock-stands, statuettes, &c. The inferior kinds only are manufactured into the 'plaster of Paris'

of the shops. The best specimens are obtained from the lower beds of the gypsum quarries, and are white, and granular, not unlike Carrara marble.

It takes a high polish; but from its softness and liability to become discoloured, articles formed of it require more careful treatment than even those of 'calcareous alabaster.'

Alabaster is wrought, turned, and fas.h.i.+oned, in a nearly similar manner to the softer varieties of marble. The tools resemble those employed for the like operations in ivory and bra.s.s. Machinery is now often applied to this purpose.

Alabaster is polished, first with pumice-stone, and then with a paste or pap made of whiting, soap, and milk or water; and lastly, with dry flannel. A better method, however, is to rub it first with dried shave-gra.s.s (equisetum), and afterwards with finely powdered and sifted slaked lime formed into a paste with water. The surface is then 'finished off' by friction with finely powdered talc or French chalk, until a satiny l.u.s.tre is produced, or with putty powder, in a similar way to marble.